1. Field of Invention
The present invention relates to flow-control supports for distributor plates in composite pressure vessels, composite pressure vessels that include a flow-control support, methods for manufacturing composite pressure vessels and methods for preparing composite pressure vessels for use in water treatment applications.
2. Description of Related Art
Composite pressure vessels are used in a variety of applications including, for example, in the treatment and/or conditioning of water (e.g., water softeners). Composite pressure vessels used in such applications typically comprise an elongate thermoplastic liner or tank that has been over-wrapped with a reinforcing layer. The elongate thermoplastic liner is typically formed of one or more olefin polymers such as polypropylene and/or polyethylene, and is fabricated into a tank structure using a blow molding, rotational molding, spin welding or other thermoplastic fabrication process. The reinforcing layer typically comprises glass filaments that are wrapped helically and circumferentially around the thermoplastic liner. The glass filaments are typically consolidated together and adhered to the thermoplastic liner using a thermosetting epoxy composition but, as disclosed in Carter et al., Pub. No. US 2006/0060289 A1, can be consolidated and adhered to the thermoplastic liner using commingled thermoplastic fibers.
In many prior art water treatment system applications, a dip tube (also sometimes referred to in the art as a distributor pipe or a supply pipe) having a distributor basket attached at one end is inserted through an aperture in a top end of the composite pressure vessel such that the distributor basket is disposed proximal to the bottom end of the composite pressure vessel. Examples of water treatment systems of this type are disclosed in Hoeschler, U.S. Pat. No. 4,228,000, Chandler et al., U.S. Pat. No. 5,147,530 and McCoy, U.S. Pat. No. 6,887,373 B2. The distributor basket in such prior art devices generally includes a plurality of narrow slits, which allow water that has flowed through water treatment media disposed in the composite pressure vessel and thereby treated to flow out of the pressure vessel through the dip tube. The slits are dimensioned to prevent water treatment media from flowing into the dip tube with the treated water. During initial assembly of such devices, once the dip tube is properly positioned within the composite pressure vessel, water treatment media is placed into the composite pressure vessel to surround the distributor basket and dip tube and hold it in position. The open end of the dip tube is then attached to a valve assembly, which is secured to the top end of the composite pressure vessel to seal off the aperture. Water to be treated is pumped into the top of the composite pressure vessel, where it flows through the water treatment media and is thereby treated. The treated water flows from the water treatment media to the distributor basket, where it passes through the slits in the distributor basket and back out of the composite pressure vessel through the dip tube to the valve assembly coupled thereto. Periodically, the flow of water is reversed to back wash and thereby condition the water treatment media.
Occasionally, it is necessary to service a composite pressure vessel (e.g., to add new water treatment media). In many cases, removal of the valve assembly disturbs the position of the dip tube. Water treatment media can settle beneath the disturbed distributor basket, making it difficult to re-secure the valve assembly to the top end of the composite pressure vessel and thus close the aperture. When this occurs, water is usually pumped at high pressure through the dip tube to flush the water treatment media away from the distributor basket until the dip tube can be properly repositioned in the water treatment media. Water pumped into the opened composite pressure vessel during this procedure flows out of the composite pressure vessel and onto the floor, where it creates a mess that can cause damage to the building structure in which the composite pressure vessel is installed. It also disturbs the water treatment media within the composite pressure vessel, which can adversely affect future water treatment performance.
Carter et al., U.S. Pat. No. 7,354,495, discloses a composite pressure vessel that utilizes one or more distributor plates (sometimes referred to therein as separators and/or fluid diffusers) instead of a distributor basket to prevent water treatment media from flowing into the dip tube during water treatment operations. The distributor plates divide the pressure vessel into regions and support the water treatment media within the composite pressure vessel. As noted in Carter et al., the distributor plates can be laser welded to the thermoplastic liner of the composite pressure vessel or can be mechanically fixed to structures within the interior of the composite pressure vessel. Prior art distributor plates have generally utilized mesh screens to prevent water treatment media from flowing through the distributor plate.